Waste-free synthesis of condensed heterocyclic compounds by rhodium-catalyzed oxidative coupling of substituted arene or heteroarene carboxylic acids with alkynes
The direct oxidative coupling of 2-amino- and 2-hydroxybenzoic acids with internal alkynes proceeds efficiently in the presence of a rhodium/copper catalyst system under air to afford the corresponding 8-substituted isocoumarin derivatives, some of which